Control channel signaling and acquisition for carrier aggregation

ABSTRACT

A method and apparatus for handling a control channel for carrier aggregation in wireless communications. The method includes determining which component carrier to listen to, detecting the downlink control channel, processing mapping information related to downlink and uplink transmissions and operating discontinuous reception with respect to carrier aggregation. The method also includes detecting a component carrier, determining the component carrier type and locating the anchor component carrier, if necessary, where the anchor component carrier carries the carrier aggregation information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/582,459 filed Oct. 20, 2009, now U.S. Pat. No. 8,705,461 issued Apr.22, 2014, which claims the benefit of U.S. Provisional PatentApplication Nos. 61/106,810 filed Oct. 20, 2008; 61/111,573 filed Nov.5, 2008; 61/142,429 filed Jan. 5, 2009; and 61/157,758 filed Mar. 5,2009, which are incorporated by reference as if fully set forth.

FIELD OF INVENTION

This application is related to wireless communications.

BACKGROUND

Long Term Evolution (LTE) supports data rates up to 100 Mbps in thedownlink and 50 Mbps in the uplink. LTE-Advanced (LTE-A) provides afivefold improvement in downlink data rates relative to LTE using, amongother techniques, carrier aggregation. Carrier aggregation may support,for example, flexible bandwidth assignments up to 100 MHz. Carriers areknown as component carriers in LTE-A.

LTE-A may operate in symmetric and asymmetric configurations withrespect to component carrier size and the number of component carriers.This is supported through the use or aggregation of up to five 20 MHzcomponent carriers. For example, a single contiguous downlink (DL) 40MHz LTE-A aggregation of multiple component carriers may be paired witha single 15 MHz uplink (UL) carrier. Non-contiguous LTE-A DL aggregatecarrier assignments may therefore not correspond with the UL aggregatecarrier assignment.

Aggregate carrier bandwidth may be contiguous where multiple adjacentcomponent carriers may occupy continuous 10, 40 or 60 MHz. Aggregatecarrier bandwidth may also be non-contiguous where one aggregate carriermay be built from more than one, but not necessarily adjacent componentcarriers. For example, a first DL component carrier of 15 MHz may beaggregated with a second non-adjacent DL component carrier of 10 MHz,yielding an overall 25 MHz aggregate bandwidth for LTE-A. Moreover,component carriers may be situated at varying pairing distances. Forexample, the 15 and 10 MHz component carriers may be separated by 30MHz, or in another setting, by only 20 MHz. As such, the number, sizeand continuity of component carriers may be different in the UL and DL.

In order to access LTE-A for DL and UL transmissions, a wirelesstransmit/receive unit (WTRU) may need to know DL and UL carrierconfigurations in terms of bandwidth, DL and UL component carrierpairings, random access parameters, and other LTE-A system specificinformation. Carrier aggregation information, such as the identity ofthe carrier, may also need to be conveyed from a base station to theWTRU. Control information with respect to carrier aggregationimplementation may be carried over a physical downlink control channel(PDCCH). The requirements for the PDCCH may need to be defined and theWTRU may need to know the time and frequency location of the PDCCH toobtain the control information.

SUMMARY

A method and apparatus for control channel signaling and acquisition inwireless communications that supports carrier aggregation. The methodincludes determining to which component carrier to listen to, detectingthe downlink control channel, processing mapping information related todownlink and uplink transmissions and operating discontinuous receptionwith respect to carrier aggregation. The method also includes detectinga component carrier, determining the component carrier type and locatingthe anchor component carrier, if necessary, where the anchor componentcarrier carries the carrier aggregation information.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 is an embodiment of a wireless communication system/accessnetwork of long term evolution (LTE);

FIG. 2 are example block diagrams of a wireless transmit/receive unitand a base station of the LTE wireless communication system; and

FIG. 3 are examples of different component carriers.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

FIG. 1 shows a Long Term Evolution (LTE) wireless communicationsystem/access network 100 that includes an Evolved-Universal TerrestrialRadio Access Network (E-UTRAN) 105. The E-UTRAN 105 includes a WTRU 110and several evolved Node-Bs, (eNBs) 120. The WTRU 110 is incommunication with an eNB 120. The eNBs 120 interface with each otherusing an X2 interface. Each of the eNBs 120 interface with a MobilityManagement Entity (MME)/Serving GateWay (S-GW) 130 through an S1interface. Although a single WTRU 110 and three eNBs 120 are shown inFIG. 1, it should be apparent that any combination of wireless and wireddevices may be included in the wireless communication system accessnetwork 200.

FIG. 2 is an example block diagram of an LTE wireless communicationsystem 200 including the WTRU 110, the eNB 120, and the MME/S-GW 130. Asshown in FIG. 2, the WTRU 110, the eNB 120 and the MME/S-GW 130 areconfigured to perform control channel signaling and acquisition for acarrier aggregation implementation.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 216 with an optional linked memory 222, atleast one transceiver 214, an optional battery 220, and an antenna 218.The processor 216 is configured to perform control channel signaling andacquisition for a carrier aggregation implementation. The transceiver214 is in communication with the processor 216 and the antenna 218 tofacilitate the transmission and reception of wireless communications. Incase a battery 220 is used in the WTRU 110, it powers the transceiver214 and the processor 216.

In addition to the components that may be found in a typical eNB, theeNB 120 includes a processor 217 with an optional linked memory 215,transceivers 219, and antennas 221. The processor 217 is configured toperform control channel signaling and acquisition for a carrieraggregation implementation. The transceivers 219 are in communicationwith the processor 217 and antennas 221 to facilitate the transmissionand reception of wireless communications. The eNB 120 is connected tothe Mobility Management Entity/Serving GateWay (MME/S-GW) 130 whichincludes a processor 233 with an optional linked memory 234.

LTE-Advanced (LTE-A) uses carrier aggregation, where a LTE-A cell iscomposed of multiple LTE carriers, each up to 20 MHz and possiblycontiguous. Carrier aggregation information may need to be conveyed froma base station to a wireless transmit/receive unit (WTRU) for downlinkand uplink transmissions.

Disclosed herein are example methods for indicating that carrieraggregation may be in use and applicable. It is noted that LTE-A mayneed to be backward compatible with LTE Release 8 and 9 and thereforeone, several, or all component carriers may support earlier LTE-basedoperation. A compatible component carrier may carry a synchronizationchannel (SCH), a broadcast channel (BCH), and other LTE channels. It isfurther noted that LTE WTRUs operating in a carrier aggregationenvironment may have no knowledge that it is in a LTE-A carrieraggregation cell. A network mechanism is used to prevent excessivehandover (HO) and cell load balancing.

One example method for conveying carrier aggregation applicability usesa broadcast channel. Compatibility with LTE means that one, several orall component carriers may carry a LTE-A BCH to inform an LTE-Acompliant WTRU about carrier aggregation. The LTE-A BCH is an extensionof the LTE BCH that does not interfere with and is compatible with LTEoperation. The LTE-A BCH carries LTE-A related cell-specific controlinformation as disclosed herein. The LTE-A related cell-specific controlinformation may be carried as a new master information block (MIB) in aLTE-A primary BCH (P-BCH) that is either in a LTE-compatible carrier oran LTE-A only component carrier. The LTE-A related cell-specific controlinformation may also be carried as a new system information block (SIB)in a LTE-A dynamic BCH (D-BCH) that is either in a LTE-compatiblecarrier or an LTE-A only component carrier.

As disclosed hereinafter with respect to example embodiments, acomponent carrier that is compatible with LTE Release 8 WTRUs may alsobe an anchor carrier, where an anchor carrier carries the LTE-A specificcontrol information. A new MIB and new SIB may be defined for thisanchor component carrier for LTE-A WTRUs. There may also be othercomponent carriers which are not compatible with Release 8 WTRUs. Thecurrent structure for LTE WTRUs may be preserved in this anchorcomponent carrier. For example, the synchronization channel andbroadcast channel that carry the MIB and SIBs may be the same as inRelease 8. The new MIB and/or SIBs that may be transmitted in thisanchor component carrier for LTE-A WTRUs may be readable only by LTE-AWTRUs. The new MIB and SIBs may be time and/or frequency multiplexedwith the LTE Release 8 MIB and SIBs. Moreover, a new radio networktemporary identifier (RNTI) may be used by the LTE-A WTRUs for the newMIB and SIBs. The MIBs and SIBs that are readable by the LTE-A WTRUs mayexist on all anchor component carriers. The new MIB and SIBs may bebased on the LTE-A WTRU class.

As disclosed hereinafter with respect to example embodiments, acomponent carrier that is compatible with LTE Release-8 WTRUs may alsobe an anchor carrier having additional SIBs that are defined on thisanchor component carrier for LTE-A WTRUs. There may also be othercomponent carriers which are not compatible with Release-8 WTRUs. NewMIB and/or SIBs may be defined in the other component carriers for LTE-AWTRUs.

In another example method, non-message based methods may be used toindicate carrier aggregation. The information about downlink componentcarriers may be implicitly carried in the synchronization channel. Forexample, the synchronization sequences that are used by a base station,such as an eNodeB, on component carriers are selected/arranged such thatwhen the WTRU detects them, these component carriers are known to beaggregated.

In another example method, existing spares codepoints may be used in theexisting MIB to indicate 40, 60, 80, etc. MHz aggregation.

In another example method, the extension bit on spares in existing MIBsmay refer to some other location that may have more detailed informationabout all the possible bandwidth configurations. For example, SIB1 orextension thereof may be used.

In another example method, LTE-A control and/or system information maybe transmitted with Radio Resource Control (RRC) signaling. In thisexample, no new MIB or SIBs are defined for LTE-A WTRUs. After a WTRUgets connected to the system, the required information may be signaledwith higher layer signaling. To reduce delay, this information can alsobe transmitted during the Random Access Channel (RACH) process, forexample, using message 4.

In another example method, the component carriers are not compatiblewith Release 8 WTRUs and are not discoverable by Release 8 WTRUs. Newsynchronization channel, MIBs and SIBs may be defined on these componentcarriers. These new channels and information are readable by LTE-AWTRUs. Auxiliary carriers may also be defined that are not discoverableby any WTRU. These may be discovered via signaling on other carriers andused as needed to increase the transmission bandwidth. Same cell ID orsome other implicit function may be used for the component carriers thatare to be aggregated. For example, when the WTRU detects the same cellID on several component carriers, it then means these carriers areaggregated. A pre-sorted list may exist for component carriers that arebeing aggregated. This list may be transmitted to the WTRU via signalingdisclosed herein.

In another example method disclosed hereinafter with respect to exampleembodiments and the uplink, the WTRU detects all or some of thecomponent carriers. The WTRU starts the random access procedure for allof the component carriers it wants to be aggregated. For example, ifthere are 5 component carriers and the WTRU wants to use only the 1stand 2nd, then random access is attempted for these two componentcarriers. For uplink carrier aggregation, RRC signalling or randomaccess messages, for example message 4, may be used.

In another example method, each component carrier is read individuallyand then tied together through comparing and matching up BCHinformation. For example, a flag may be used on the BCH to indicate thatthis component carrier is a part of an aggregation. In this case,redundant MIB information that may transmitted on MIB on each individualcomponent carrier, such as most significant (MSB) of sequence framenumber (SFN), may need to be consolidated.

In another example method, a component carrier may be LTE Release 8 WTRUcompatible and part of an aggregate. However, it does not carry an LTE-AP-BCH. The component carrier may be part of a slave/master scheme wherethe component carry may broadcast an offset, such as for example, apairing distance to a master component carrier. The offset may be usedas a flag that points at a component carrier that provides the LTE-A BCH(e.g., the master).

For each of the examples discussed herein and as disclosed with respectto the example embodiments, if an LTE-A WTRU camps on a componentcarrier that does not carry the LTE-A system information, the WTRU maybe redirected to a component carrier that carries the LTE-A systeminformation.

As such, the LTE-A WTRU may receive information regarding whichcomponent carrier(s) to listen to for downlink control information fromthe LTE-A BCH, or L1 or L2/3 signaling.

Disclosed hereinafter are example methods for detecting the downlinkcontrol information. The WTRU then may detect its downlink controlchannel among all candidates by using blind detection, where candidatesare all possible control channels among which one or more target thespecific WTRU. As stated herein, a downlink control channel may be aphysical downlink control channel (PDCCH) that may be used to send LTE-Acontrol information. When multiple PDCCHs are used for componentcarriers, for example when there is one PDCCH per component carrier, thenumber of blind detections increases remarkably with the number ofPDCCHs. The number of blind detections can be reduced by limiting theWTRU-specific search space. This search space is signaled to the WTRU byhigher layer signaling. To reduce the number of blind detections andhigher layer signaling overhead, the same search space may be used inall component carriers, such as for example, the search space used inthe primary carrier.

Disclosed hereinafter are examples of what the control information mayindicate. In an example, the LTE-A control information may indicate thelocation of downlink data grants for LTE-A WTRUs. In an exampleembodiment, the location of the downlink data grants may be in the samecomponent carrier in which the control information was received. Inanother example embodiment, the location of the downlink data grants maybe in a different component carrier than that in which the controlinformation was received. In another example embodiment, if multiplecomponent carriers are used to carry the location of the downlink datagrants, the location of the downlink data grants may or may not beincluded in the same component carrier in which the control informationwas received.

The downlink data grants may indicate a pre-grant. For example, in atransmission time interval (TTI) before the actual grant, the WTRU mayreceive the pre-grant which tells the WTRU that an actual grant will betransmitted in the next TTI. The pre-grant may also indicate on whichcomponent carrier(s) the data may be sent. In this way, the LTE-A WTRUcan reduce the memory needed to buffer downlink data that is for otherWTRUs.

The WTRU may be configured to handle downlink data grants that mayarrive one or more symbols prior to arrival of the data. The LTE-Asub-frame may have control symbols positioned earlier than in LTE topermit lower complexity WTRU operation.

Disclosed hereinafter are examples with respect to the physical downlinkcontrol channel (PDCCH) and how it may be mapped to component carriersdepending on at least the size of the total aggregated bandwidth, thenumber of component carriers and other factors disclosed herein.

In an embodiment, the WTRU is configured to handle the scenario when thesizes of the component carriers are different and the sum is less thanor equal to the maximum LTE bandwidth of 20 MHz (e.g., two carriers of10 MHz and 5 MHz; or two carriers of 10 MHz each). One PDCCH formultiple component carriers may be used. For example, one PDCCH for(10+10) MHz may use the same control channel formats as in LTE.

In another embodiment, one control channel, e.g., the PDCCH, may be usedfor a group of multiple downlink component carriers, including as manyas all the available component carriers. The PDCCH may be transmitted inone of the multiple downlink component carriers. The WTRU is configuredto detect the PDCCH without having to search in all of the othercomponent carriers of the group. As necessary, the PDCCH may be shiftedto another component carrier, the location of which is communicated tothe WTRU by L1 or L2/L3 signaling or based on implicit mapping derivedfrom the sequence frame number (SFN), TTI index, WTRU ID, etc.

In some cases, the same frequency resources may be used in all or someof the component carriers. For example, for WTRUs with peak data raterequirements, it may be possible that all or most of the resources onall component carriers will be used for both downlink or uplinktransmissions, or that wideband CQI is reported by the WTRU. The sameresources on multiple component carriers may also be used for frequencydiversity, by coding and distributing the transmission over multiplecomponent carriers (and within component carriers), repeating the samedata on those resources in different component carriers, using differentredundancy versions in different component carriers, or when hoppingover the component carriers.

When using a PDCCH per component carrier approach, it is unnecessary tosend separate PDCCHs for all component carriers. If the same HARQprocess is used for the component carriers, it may be indicated by L1 orL2/L3 signaling that the one PDCCH is used for all or some subset of thecomponent carriers. If separate HARQ processes are used for thecomponent carriers, smaller PDCCH formats may be used for the othercomponent carriers. These formats do not need to carry commoninformation, such as resource allocation, MIMO information, etc.

When one PDCCH is used for multiple component carriers (including all),it may be indicated by L1 or L2/L3 signaling. The PDCCH format includescommon information, e.g., resource allocation, MIMO, etc., that isapplied to all component carriers.

In the case that component carriers are different sizes, the sameallocation may be possible for all operating component carriers.Therefore, a rule is needed for the WTRU and the base station on how tointerpret the allocation in other component carriers. For example, ifthe PDCCH in component carrier A indicates that resource blocks (RBs)50-100 are used, but in the attached component carrier, componentcarrier B, where the allocation is to be copied, there are only 75 RBs,the allocation for component carrier B has to be determine. In thiscase, the rules may determine that component carrier B should use RBs50-75, or use RBs 25-75.

The mapping between the PDCCH and the component carriers used totransmit a shared data channel, for example a physical downlink sharedchannel (PDSCH), may be done by higher layer signaling, L1 signaling(the PDCCH then also carries the indices of the carriers), and/orimplicitly by the component carrier that transmits the PDCCH. When L1signaling is used to indicate for which carrier the resource allocationinformation in the downlink grant is for, the PDCCH field that carriesthe index/indices of the carrier(s) may be referred as the carrierindicator field. After decoding the PDCCH, the WTRU would use theindicated carrier(s) to receive downlink transmission.

In a LTE downlink sub-frame, the first orthogonal frequency divisionmultiplexing (OFDM) symbol may contain a physical control formatindicator channel (PCFICH) and the first one to K orthogonal frequencydivision multiplexing (OFDM) symbols may be used to transmit controldata (e.g., K may be up to the first four OFDM symbols, but is notlimited to this number), and the remaining OFDM symbols may be used fordata transmission. The number of OFDM symbols used to transmit controldata is signaled in the PCFICH. A PCFICH may signal zero to K OFDMsymbols which are used to carry control data. In embodiments whichinclude a PDCCH in a component carrier, the PDCCH may be carried in thesame or a different component carrier than the one for which the PDSCHis scheduled. When the PDCCH is transmitted in another componentcarrier, the WTRU still needs to know how many OFDM symbols are used forcontrol data in the target component carrier (which has the PDSCH) forcorrect decoding. Therefore, the following restrictions apply. ThePCFICH is always transmitted in all component carriers regardless of thelocation of the PDCCHs. Therefore, there may be an independent controlregion size per component carrier.

When the WTRU detects a PCFICH in a component carrier, the number ofOFDM symbols, as indicated by the PCFICH, used for control datatransmission in the target component carrier is decoded. This includesthe possibility for zero OFDM symbols for control data transmission.

In another embodiment, the PCFICH for all or several component carriersmay be transmitted in one of the component carriers, for example aprimary component carrier. In this way, the WTRU may be indicate thenumber of PDCCH symbols in each component carrier, and it may alsodetermine the number of data symbols in each component carrier as well.

The eNodeB transmits a PCFICH in one or more component carriers toindicate how many PDCCH symbols are present in one or more componentcarriers. The eNodeB will indicate a zero length PDCCH region byspecifying a zero length PDCCH region, hereafter called a PDCCH-lesscomponent carrier, in the corresponding PCFICH. A component carrierwhich has a zero length PDCCH region must be associated with a componentcarrier that has a PDCCH present by the eNodeB. The eNodeB will indicatea PDCCH-less component carrier to increase the available resource blocksfor PDSCH data transmission to a WTRU.

Disclosed herein are methods for signaling carrier componentconfiguration. In general, the number of uplink and downlink componentcarriers, respectively, is limited. Alternatively, the allowedcombinations (in terms of the aggregated number and/or uplink/downlinkpairing) are limited and the configuration is signaled via BCH (in cellspecific asymmetric aggregation case) or L2/3 signaling (in WTRUspecific asymmetric aggregation case).

When the number of downlink component carriers is different than that ofuplink component carriers, (that is, asymmetric uplink/downlinkcomponent carrier aggregation for the PDCCH signaling), any of thedisclosed methods herein may be used for PDCCH signaling. For theasymmetric uplink/downlink case, the size of each component carrier andthe number component carriers may not be the same in the downlink or theuplink. In addition, the number of uplink and downlink componentcarriers may not be the same. For a given WTRU in this case, the numberof active component carriers may be less than the total in either theuplink or downlink. In the “self contained” approach disclosed herein,it may be natural to have a single uplink component carrier associatedwith each downlink component carrier and some uplink component carriersmay be associated with more than one downlink component carrier.WTRU-specific uplink/downlink pairing may also be used for loadbalancing (e.g., consider 3 downlink and 2 uplink component carriers).Cell specific uplink/downlink pairing may result in more loads on agiven uplink component carrier than WTRU-specific uplink/downlinkpairing (e.g. consider the case of 3 uplink component carriers where oneuplink component carrier is used by all the WTRUs).

Disclosed hereinafter are example methods for uplink configuration withrespect to carrier configuration. In LTE-A, the eNodeB will determinethe uplink resource assignment based on received WTRU feedback, networkload and other information. The uplink scheduling grant will be signaledto the WTRU via downlink control information (DCI) on the PDCCH. Theterms DCI and PDCCH may be used interchangeably. As disclosed herein,carrier aggregation is important in LTE-A in order to support downlinktransmission bandwidths larger than 20 MHz, e.g. 100 MHz. The mapping ofuplink (UL) scheduling grants (which is also carried on the PDCCH) isalso important because carrier aggregation is used in UL, and thepossibility of UL/DL asymmetric carrier aggregation will make mappingdifficult. The asymmetry applies to both carrier size and number ofcarriers, i.e., a 20 MHz DL carrier may be paired with two 5 MHz ULcarriers.

The UL scheduling grant signaling carried in the PDCCH plays a criticalrole in carrier aggregation. UL scheduling grant signaling may depend onthe aggregation levels for medium access control layer (MAC) and on theaggregation levels for the physical layer (PHY). In addition, backwardcompatibility with respect to LTE Release 8 needs to be considered.

In an embodiment, a method for mapping the uplink grant for each ULcarrier to a single DL carrier regardless of the UL/DL asymmetry isdisclosed. Mapping the uplink grant may be fixed for all possible UL/DLaggregation scenarios. Mapping may be fixed or semi-static. The mappingmay be done by WTRU specific signaling or by cell specific higher layersignaling. When there are multiple DL component carriers, the UL grantis hopped over different DL carriers in different TTIs. The hoppingpattern may be signaled to the WTRU by cell specific signaling or byWTRU specific higher layer signaling. Alternatively, the hopping mayalso be determined by a predefined rule, such as circular shift usingmodulo operation.

If the UL Grant mapping is indicated to the WTRU using either specificsignaling, or higher layer signaling, and the WTRU reads this signalingusing a semi-static procedure, the WTRU decodes the UL grant in theindicated component carrier when received.

If determined by a predefined rule, the WTRU uses a modulus operation todetermine the hopping pattern for the UL grant. Once determined, theWTRU decodes the UL grant in the indicated component carrier.

The UL grant for each UL component carrier or for each UL hybridautomatic repeat request (HARQ) entity may be independently encoded andmapped to a corresponding DL component carrier(s). In the case wherespatial multiplexing is used in the uplink, several codewords that arespatially multiplexed on the same time-frequency resources may becontrolled by one HARQ entity. Alternatively, the UL grants for multipleUL component carriers (or UL HARQ entities) may be jointly encoded andmapped to a single DL component carrier. Alternatively, the jointlyencoded UL grants may be spread over multiple DL component carriers.

In another embodiment, a method for mapping the uplink grant for all ULcomponent carriers on to one DL component carrier for the asymmetriccase is disclosed. The UL grant needs to carry control information for aset of UL component carriers. For a fixed mapping between the uplinkscheduling grant and corresponding uplink component carriers, themapping is signaled either by WTRU specific signaling or by cellspecific higher layer signaling. When WTRU-specific signaling is used, amapping between WTRU-specific parameter(s) and UL component carrierindex is necessary. A mapping using WTRU ID or the like to UL componentcarriers may also be used. When there is one uplink component carrierper uplink grant for a WTRU, then the uplink grant does not need tocontain the index of the uplink component carrier. When one uplink grantassigns resources on several component carriers, the resource allocationfield in the uplink grant may include uplink component carrier indicesor extended RB indices span over several component carriers. When adynamic mapping between uplink scheduling grant and corresponding uplinkcomponent carriers is used, the uplink component carrier indexinformation may be signaled in the uplink scheduling grant. A bitmapmapping to UL component carriers associated with the UL grant may alsobe used. Other mapping methods may also be utilized.

Multiple UL scheduling grant components are combined into an aggregatedUL grant, each component grant corresponding to a separate UL componentcarrier. However, common information (including UE ID) may be sharedamong UL grant components in the aggregated UL grant (signaled onlyonce) to save signaling overhead.

One uplink grant exists for all or some of the component carriers. Whenclustered discrete Fourier transform spread orthogonal frequencydivision multiple a access (DFT-S-OFDMA), N×single-carrierfrequency-division multiple access (SC-FDMA), or a hybrid of clusteredDFT-S-OFDMA and N×SC-FDMA is used as the multiple access scheme, oneuplink grant could allocate resources on several component carriers. Asan example, component carriers that are combined with a single discreteFourier transforms-inverse fast Fourier transform (DFT-IFFT) pair (e.g.,contiguous carriers) in the SC-FDMA air interface may be addressed witha single grant.

Downlink control information (DCI) formats for granting UL resources areextended to treat the aggregate UL bandwidth (BW) in the componentcarriers to be used as a single component carrier of the combined size(e.g., if two 5 MHz component carriers are associated with an UL grant,the DCI format corresponds to a 10 MHz component carrier, where the DCIformat has the size it would have if there was a single 10 MHz ULcomponent carrier). The ordering of component carriers and the resourceblocks (RBs) across the aggregation may be inferred from their carrierfrequency signaled in BCH, in the WTRU or from cell specific signaling.For aggregated BW greater than 20 MHz, the extension of the DCI formatcorresponds to the aggregated BW. For example, if the aggregation is20+10 MHz, the DCI format would correspond to that of a single band with30 MHz.

DCI formats for granting UL resources include a set of common fields anda set of component carrier-specific (or component carrier groupspecific) fields. It may require a second cyclic redundancy check (CRC)for group-specific common control channel. All or some of the followingparameters may be common for all component carriers: modulation andcoding set (MCS), precoder(s), number of layers, number of codewords,frequency hopping, distributed virtual resource block (DVRB). RBallocation per component carrier may be different. Alternatively, allparameters are common (e.g., resource allocations are imaged or mirroredin all or some of the component carriers).

The downlink component carrier which all uplink component carriers aremapped on to may be configured by higher layer signaling.

In another embodiment, a method for mapping the uplink grant on to a(possibly different) pre-determined component carrier is disclosed. Themapping between UL and DL component carriers is both specified and fixedin the standards (no extra signaling is needed), signaled by WTRUspecific signaling or by cell specific higher layer signaling.

If more than one uplink component carrier is mapped to a downlinkcomponent carrier, the UL grant needs to carry control information ofthe UL component carrier indices. The methods disclosed herein formapping the uplink grant for each UL component carrier to a single DLcomponent carrier regardless of UL/DL asymmetry may be used for thisembodiment as well.

In the situation where there are physical downlink channels (PDCCHs) inall or some of the downlink component carriers, the WTRU may check thesecarriers to see if PDCCH exists with different frequencies. A primarydownlink component carrier is that carrier which the WTRU may initiallycamp on. The WTRU may only read the primary downlink component carrier,and may read the other component carriers when commanded using eithercarrier indication or higher layer signaling. For example, when aneNodeB requests the WTRU to transmit data on an uplink component carriermapped to a downlink component carrier which is not the primarycomponent carrier, the uplink grant will be carried on that downlinkcomponent carrier. Two embodiments are disclosed to address thissituation. In an embodiment, where there is a default uplink componentcarrier and an associated downlink component carrier, the WTRU alwaysmonitors the downlink component carrier, which could be the primarycomponent carrier or a different one. In another embodiment, the DRXprocedures designed for downlink component carrier disclosed hereinapply to this situation as well, i.e., uplink grant is also carried by aPDCCH, and the same DRX procedures apply.

Multiple UL grants that are used for one WTRU are simultaneouslytransmitted in a single (or multiple) DL component carriers withmultiple PDCCHs. The WTRU has multiple WTRU IDs to distinguish which ULgrant maps to which UL component carrier. The mapping between WTRU IDsand component carrier is determined by the network and signaled byhigher layers. Some WTRU IDs may correspond to multiple UL componentcarriers and the granting methods disclosed herein are used to interpretthe grant.

Disclosed hereinafter are example methods for discontinuous reception(DRX) operation in LTE-A with carrier aggregation.

In an embodiment, the WTRU is configured to be active in one or more butnot all component carriers (i.e., the WTRU has either uplink or downlinktransmissions). The other component carriers are idle and the WTRU doesnot try to detect any control information on those DL componentcarriers. A separate PDCCH may be sent for each component carrier. Ifthe WTRU is scheduled on the other component carriers, it is informed byL1 or L2/L3 signaling on the current component carrier on which it isactive. After reception of the signaling, the WTRU attempts to detectthe PDCCH on the other component carriers. The time between thereception of the signaling (when it is scheduled on other carriers) andthe transmission of the PDCCH on the other carriers may bepre-determined. With such a mechanism, DRX is used only on one of theactive component carriers, for example the primary component carrier.

In a self contained scenario where there each component carrier has aPDCCH, and there is a PDSCH per carrier per PDCCH, a DRX may be used percomponent carrier to more flexibly reduce the WTRU power consumption byreducing the ON duration of component carriers that are not used asoften compared to the ON duration of the most used component carriers.Current DRX procedures do not permit a zero ON duration since it wouldnot make any sense in a single carrier system. With a multi componentcarrier system, the ON duration is allowed to go to zero on all but onecomponent carrier to more fully take advantage of DRX power reductions.Accordingly, the DRX parameter range may include a zero ON duration orinfinite DRX sleep time. DRX procedures that are set up for onecomponent carrier may be set up via communication on the other componentcarriers so that the WTRU can be informed to start listening again to acomponent carrier that previously had a zero ON duration. For example,an radio resource control (RRC) signaling may be carried on componentcarrier A to set up the DRX procedure on component carrier B.

The DRX behavior on some component carriers may be affected by thereception of a PDCCH in another component carrier. During the ONduration of a DRX cycle in carrier A, the WTRU may get a PDCCH while thebase station is ready to start a high data transmission with multiplecomponent carriers, but the DRX cycle on the other component carriers islong or has a zero ON duration. The reception of a PDCCH on componentcarrier A causes the WTRU to change DRX behavior on other componentcarriers. For example, the WTRU monitors the next N sub-frames incertain other (or all) component carriers). As another example, the WTRUfalls back to a different DRX cycle with higher ON duration probabilityfor a predetermined time. The WTRU may also monitor a predefined patternof component carriers for the PDCCH for a predefined time.

Alternatively, a 2-D DRX pattern may be defined over the entireaggregation or a subset of it. Rather than a per-carrier DRX procedures,a single multi-carrier DRX pattern may be defined by a duration andlocation of ON durations in all component carriers that the WTRU is tomonitor.

To maintain backward compatibility with LTE Release 8, all componentcarriers are configured such that they can support Release 8 compatibleWTRUs. Each component carrier may be configured as disclosed herein. Inan embodiment, in each carrier, Release 8 PDCCH and LTE-A PDCCH aremultiplexed in a code divison multiplexing (CDM) manner. In this case,the spreading (or masking) code may be derived based on WTRU ID that isthe radio network temporary identifier (RNTI).

Disclosed herein are example methods for addressing compatibilitybetween LTE Releases and LTE-A. In an embodiment, in each carrier,Release 8 PDCCH and LTE-A PDCCH are multiplexed in a frequency divisionmultiplexing (FDM) manner. Alternatively, an LTE-A network may reservecertain resource allocation portions of the bandwidth for LTE-A WTRUs.

In another embodiment, in each carrier, Release 8 PDCCH and LTE-A PDCCHare multiplexed in a time division multiplexing (TDM) manner such thatLTE-A PDCCH is transmitted in different OFDM symbols.

In another embodiment, in each carrier, Release 8 PDCCH and LTE-A PDCCHare multiplexed in a TDM manner such that LTE-A PDCCH is transmitted inTTIs—e.g., some sub-frames are LTE and some are LTE-A. DRX may be usedto manage separation between the two types so that LTE WTRUs don't tryto decode LTE-A PDCCHs.

In another embodiment, in each carrier, multiplexing Release 8 PDCCH andLTE-A PDCCH in a hybrid FDM/TDM manner such that LTE-A PDCCH istransmitted in different resource elements (REs).

Disclosed hereinafter are example embodiments with respect to signalingand acquisition. FIG. 3 illustrates the different types of componentcarriers that may be applicable in the example embodiments and aredisclosed herein for illustrative purposes.

In general, in a first example embodiment there is only one LTE-Acomponent carrier which carries the LTE-specific system information andthis component carrier is called either the primary or anchor componentcarrier. The terms primary or anchor component carrier may be usedinterchangeably to mean the same thing. By configuration, the designatedanchor carrier may provide system information, synchronization andpaging for a certain cell. A non-anchor carrier may not have the LTE-Aspecific broadcast channel but may have the synchronization channel. Theremaining LTE-A component carriers, (the non-anchor carriers), may notcarry the LTE-A system information. The non-anchor component carriersmay not have synchronization channels so they are not detectable by theWTRU, except in two situations. In a first exception, if a non-anchorLTE-A component carrier supports Release 8 WTRUs, the non-anchor LTE-Acomponent carrier has the Release 8 synchronization channel and theRelease 8 broadcast channel. This is shown as Type 2 in FIG. 3. In asecond exception, if a non-anchor Release 8 carrier does not supportLTE-A functionalities but has some LTE-A specific system information, ithas the Release 8 synchronization channel and the Release 8 broadcastchannel. This is shown as Type 6 in FIG. 3.

A second example embodiment may have several anchor carriers in an LTE-Asystem. In addition to the anchor component carrier, there may beRelease 8 carriers. The Release 8 carrier may be “Release 8 componentcarriers without LTE-A functionality”, shown as Types 5 and 6 in FIG. 3or backward compatible LTE-A component carriers that support Release 8functionality, shown as Types 1 and 2 in FIG. 3. Type 5 and Type 6component carriers do not support LTE-A functionality such as moreadvanced multiple-input multiple-output (MIMO) techniques, cooperativecommunications, LTE-A specific control channels, etc. Type 6 componentcarriers may have some additional information transmitted, for examplein the broadcast channel, and this information is transparent to Release8 WTRUs. It should be understood that, Release 8 backward compatibleLTE-A component carriers support both Release 8 and LTE-Afunctionalities.

Moreover, there may also be Release 8 non-backward compatible LTE-Acomponent carriers, shown as Types 3 and 4 in FIG. 3 and auxiliarycarriers. Type 3 and 4 component carriers are not backward compatibleand are not used by Release 8 WTRUs. Auxiliary carriers are discoverableneither by Release 8 nor LTE-A WTRUs and may be configured by the basestation for usage as additional bandwidth. The non-anchor, Release 8non-backward compatible LTE-A component carriers, shown as Type 4 inFIG. 3, are not detectable by the WTRUs.

Both Release 8 and LTE-A carriers use the same synchronization channeland techniques. This means that the WTRU may not differentiate these twotypes of carriers by using the synchronization channel. The anchorcomponent carrier may be either Release 8 backward compatible ornon-backward compatible.

In general, after the WTRU detects one of these carriers during thesynchronization phase, it needs to get the LTE-A specific systeminformation. This information is transmitted on the broadcast channel ofthe anchor carrier(s) only. Therefore, the WTRU needs to detect theanchor carrier and read the system information on this carrier.Disclosed hereinafter are anchor carriers that address the mechanismsand procedures via which the WTRU locks on to the anchor carrier;determines whether or not a carrier is the anchor; receives thetransmitted LTE-A specific system information and determines the type ofinformation carried by the anchor carriers.

An example embodiment of an LTE-A signaling and acquisition with asingle anchor component carrier will now be disclosed. The exampleembodiment has a single anchor carrier in the LTE-A system and only thiscarrier may carry the LTE-A specific system information.

The example embodiment has two phases. A first phase relates to the WTRUlocking on to the anchor carrier. The second phase relates totransmission of LTE-A specific system information. Both aspects aredetailed below.

During the first phase or synchronization phase, the LTE-A WTRU locksonto any of the carriers because the WTRU sweeps a frequency band untilit successfully finds a synchronization channel. The LTE-A WTRU may lockonto one or more of the following carriers: component carriers withRelease 8 compatibility, such as type 1, 2, 5, or 6, and anchor LTE-Acomponent carriers such as Release 8 backward compatible Type 1 andRelease 8 non-backward compatible Type 3.

The first phase may have two aspects. The first aspect is concerned withdetermining the type of carrier once the WTRU finds the componentcarrier. The WTRU determines whether or not the carrier is the anchorcarrier. The second aspect comes into play if the WTRU learns that thecomponent carrier is not the anchor carrier. The second aspect providesmethods for finding the anchor carrier and mechanisms for directing theWTRU to the anchor carrier.

With respect to for learning about the type of component carrier, thereare several example methods. In a first example method, the informationindicating the type of the component carrier is transmitted in the BCH.The WTRU reads the BCH MIB, SIB, or both MIB and SIB. The WTRU decodesthe BCH, gets the information, and learns the type of the componentcarrier. In a component carrier configured in a mode that supportsRelease 8 WTRUs, the anchor carrier information may be included in anextended MIB or SIB that may not be read by Release 8 WTRUs.

Specifically, the indication of the type of the carrier may be carriedin the BCH by defining a new entity similar to a MIB or SIB. The WTRUknows the location of this entity in time/frequency and reads thisinformation in that location. The new entity may be frequency and/ortime multiplexed with the Release 8 BCH entities. It may also be encodedwith a new radio network temporary identifier (RNTI). This informationmay not result in a large overhead and is only an indication of the typeof the carrier. For example, the new entity may be carried in thecentral x radio blocks (RBs) of the 1.25 MHz bandwidth, and on theorthogonal frequency division multiplexing (OFDM) symbol next to thephysical broadcast channel (PBCH) or any other fixed timing relative toPBCH, physical synchronization channel P-SCH, etc., where x is less than6. This indication may also be encoded in a new type of Release 8 SIB oras an extension to the existing SIBs.

The WTRU decodes the new entity which is carried on a fixedtime/frequency location. After decoding the new entity, the WTRU learnsthe type of the component carrier. The WTRU may get this information bydecoding a newly defined Release 8 SIB or an extension to one or some ofthe existing Release 8 SIBs.

According to another method, the WTRU performs a random access procedureon the uplink carrier or one of the uplink carriers linked with thedetected downlink component carrier and gets a radio resource control(RRC) connection. The WTRU then receives the information regarding theanchor carrier through higher layer signaling if it supports carrieraggregation.

Specifically, the indication of the type of carrier and other relevantinformation may be transmitted to the WTRU after the RRC connection. TheLTE-A WTRU locks onto a carrier and gets an RRC connection. If thiscarrier is also the anchor carrier, all LTE-A system information may betransmitted to the WTRU with RRC signaling. If this carrier is not theanchor carrier, the location of the anchor carrier may also betransmitted to the WTRU by RRC signaling. In this case, the WTRU learnsthe type of the component carrier and possibly the location of theanchor carrier with higher layer signaling. Alternatively, the RRCsignaling from the non-anchor carrier will transmit all LTE-A systeminformation, from where the WTRU will learn the anchor carrier. Notethat in this RRC-based method, the anchor carrier may be eithercell-specific or WTRU-specific.

The WTRU may also learn the type of the carrier during the random accessprocedure. For example, the type of carrier may be transmitted inmessage 2 or 4. The WTRU decodes the particular message and learns thetype of the carrier or the anchor carrier is directly indicated in themessage. Note that in this Random Access Channel (RACH)-based method,the anchor carrier may be either cell-specific or WTRU-specific.

In another method, several bits of the spare bit string may be used toindicate the type of the component carrier. The bit string is ignored bythe Release 8 WTRUs, so this additional information inserted into theMIB is transparent to these WTRUs.

For example, a single bit may be used to indicate if a component carrieris the anchor carrier or not. The structure of the master informationblock in Release 8 is illustrated in Table 1 below. The MIB consists ofthe downlink bandwidth, Physical Hybrid Automatic Repeat RequestIndicator Channel (PHICH) configuration and system frame number. Inaddition to these, there is a reserved spare bit string. Also, there aretwo spare codepoints in the downlink bandwidth region.

TABLE 1 MasterInformationBlock -- ASN1START MasterInformationBlock ::=SEQUENCE { dl-Bandwidth ENUMERATED { n6, n15, n25, n50, n75, n100,spare2, spare1}, phich-Configuration PHICH-Configuration,systemFrameNumber BIT STRING (SIZE (8)), spare BIT STRING (SIZE (10)) }-- ASN1STOP

The remaining spare bits may be used to transmit some LTE-A specificsystem information. For example, the number of downlink componentcarriers, uplink component carriers, and how they are linked may besignaled with the remaining spare bits.

The remaining spare bits may also indicate where to locate the anchorcarrier. If the number of the bits are not enough to indicate theabsolute location of the anchor carrier, these bits may be used toindicate the RB allocation (i.e., address of a time/frequency resource)of a Physical Downlink Shared Channel (PDSCH) which contains theinformation of the anchor carrier location.

After successfully completing the synchronization procedure, the WTRUdecodes the MIB. If the WTRU is a Release 8 WTRU, the WTRU ignores thespare bits in the MIB. If the WTRU is an LTE-A WTRU, the WTRU interpretssome of the bits unused by a Release 8 WTRU in the MIB (specified asaforementioned) as the type of the component carrier. If the carrier isan anchor carrier, the WTRU knows the location of the LTE-A specificsystem information and reads the LTE-A specific system information. Ifthe carrier is not an anchor carrier, the WTRU gets information thatindicates the location of the anchor carrier. The WTRU may get thisinformation by decoding some or all of the remaining spare bits.Alternatively, the WTRU will receive resource block (RB) allocation of aPDSCH that contains information of the anchor carrier location.

Another method uses a new cyclic redundancy check (CRC) masking sequenceto mask the CRC of PBCH in LTE-A and the LTE-A WTRU will use the newmasking sequence to decode the BCH. If the carrier is Release 8non-backward compatible and is also the anchor carrier, (i.e. a Type 3),then this indication is implicit because the new BCH (and maybe thesynchronization channel) may only be detectable by the LTE-A WTRUs. Inthis case, the LTE-A WTRU has to know that the BCH (or thesynchronization channel) is LTE-A specific. This may be achieved, forexample, by masking the BCH with a new cyclic redundancy check (CRC)masking sequence. The LTE-A uses this new CRC masking sequence to decodethe BCH.

In another example method, if the anchor carrier is a Release 8non-backward compatible LTE-A carrier (a Type 3), the LTE-A physicalbroadcast channel (PBCH) should be masked with a special CRC (e.g.,ANCHOR_CRC) and successful decoding of such PBCH indicates the anchorcarrier. In this example, the WTRU performs synchronization proceduresand decodes the PBCH to obtain the information of carrier type. Whendecoding the PBCH, the WTRU de-masks the PBCH with corresponding CRCs.If the WTRU is a LTE-A WTRU, it will de-mask the PBCH with the specialCRC (e.g., ANCHOR_CRC) and regular CRC (as in LTE Rel-8). If the CRCtest succeeds with the special CRC, the anchor carrier is indicated. IfCRC test fails with the special CRC but succeeds with the regular CRC,this indicates that the WTRU has not found the anchor carrier and hascamped on a non-anchor component carrier. In this case, the WTRU mayread the PBCH, may receive a SIB via RRC signaling and get directed tothe anchor carrier if a Release 8 backward compatible carrier (Type 2)or a Type 6 carrier is the component carrier the WTRU has camped on.Further, the WTRU may continue the synchronization procedures and decodethe PBCH for the next carrier. The procedure restarts with the WTRUperforming the synchronization procedures and decoding PBCH forcarriers.

If the WTRU is a Release 8 WTRU, it will de-mask the PBCH with theregular CRC only. The WTRU will not pass the CRC test for the carrierwhere the PBCH is masked with the special CRC. Therefore the WTRU willnot access the LTE-A only carrier.

Disclosed are methods for directing the WTU to the anchor carrier. TheWTRU is directed to the anchor carrier after the WTRU learns that thecomponent carrier is not the anchor carrier. The WTRU is directed to theanchor carrier by either signaling in the BCH, higher layer signalingafter RRC connection setup or signaling during the random accessprocess.

In an example method, the WTRU may be directed to the anchor carrierwith RRC signaling. After the WTRU gets an RRC connection, the WTRU maylearn the location of the anchor carrier with higher layer signaling.After the WTRU gets this information, it moves to the anchor carrier andattempts to decode the BCH on the anchor carrier to receive the systeminformation.

The WTRU may also learn the location of the anchor carrier during therandom access procedure. For example, the location of the anchor carriermay be transmitted in message 4 and the WTRU decodes this message andlearns the location of the anchor carrier.

A new entity that contains the information of the component carrier typemay be employed. This entity may also carry the location of the anchorcarrier. The same procedures outlined hereinabove may similarly be usedby the WTRU. It may also be possible to have a new entity that onlycontains the location information of the anchor carrier. The WTRU learnsthe location of the anchor carrier by decoding this entity and thenmoves to the anchor carrier. This entity is not necessarily transmittedon the anchor carrier if there is a single anchor carrier.

Depending on the selected method, the directing-to-anchor-carriermechanism may be used only on the non-anchor carriers. For example, ifthe type of carrier and location of the anchor carrier are codedseparately and transmitted on two different entities, then the locationinformation may need to be transmitted only on the non-anchor carriers.

The WTRU may also continue cell search until the anchor carrier isdetected.

The directing command may be encoded in a new type of Release 8 SIB oras an extension to the existing SIBs. The LTE-A WTRU knows thisextension SIB and learns the location of the anchor carrier by decodingthis SIB or the directing command may be encoded in the Release 8 MIB byusing the spare bit string.

The location of the anchor carrier and other possible information aboutthe anchor may be transmitted in the sub-frames regarded as blank forthe LTE-A WTRUs. Accordingly, after learning the location of the anchorcomponent carrier, the WTRU moves to that carrier.

Disclosed hereinafter are example methods for transmission of the LTE-Aspecific system information. After the WTRU finds the anchor carrier,the new system information needs to be transmitted on the anchorcarrier. The example methods for this transmission depend on whether thecarrier is Release 8 backward compatible or not.

In the case of a Release 8 compatible anchor carrier, the Release 8 BCHis kept intact. The new information may be transmitted in new MIBs andSIBS or in extensions to the existing ones. Several methods for definingnew MIB/SIBs or extensions to these are disclosed hereinafter.

For LTE-A, the primary broadcast channel may be extended either in thefrequency domain or the time domain. As an example for frequency domainextension, N sub-carriers in addition to the current 72 sub-carriers maybe used. The newly allocated subcarriers may be located either adjacentto the current center subcarriers or offset by a fixed number ofsub-carriers from the center subcarriers.

As an example for time domain extension, the BCH may be transmitted onthe same frequency as the Release 8 broadcast channel, however, it willbe transmitted with more OFDM symbols than the current 4 for the MIB andmore subframes in the SI-window for other SIBs. If such anaddition/extension is used, the WTRU may know the time/frequencylocation of the new entity. The WTRU reads the new system information inthis fixed location and decodes it to receive the LTE-A specific systeminformation.

The LTE-A specific system information may be made as an extension toinformation elements (IEs) in existing Release 8 SIBs or systeminformation messages (SIs). Different ASNI formats for Release 8 andLTE-A would enable the LTE-A WTRU RRC to receive the relevant contents.For example, the LTE-A WTRU RRC may receive the carrier specific uplinkanchor information IE as the criticalExtension-Rel10 specific for LTE-Ain the regular Release 8 SIB-2 and therefore act on the information touplink access, while the criticalExtension-Rel10 is transparent toRelease 8 WTRUs. Further, LTE-A specific system information may beextension SIBs which will go to a separate SI and SI-window for LTE-Aonly. For example, all LTE-A specific operating parameters in the cellmay be made into one or more separate SIBs, i.e. SIB-12, SIB-13, withthe SIB for LTE-A cell configuration and uplink access assigned to ashort periodicity as is the regular Release 8 SIB-2 and the rest of theLTE-A SIBs with longer periodicities. An LTE-A WTRU accessing theRelease 8 compatible carrier may read the MIB, (which will know theLTE-A cell property), then read the SIB-1 to find the overall SIBscheduling and the LTE-A specific SIBs, i.e. SIB-12 and SIB-13, based onthe scheduling information found in SIB-1 for the LTE-A systeminformation acquisition.

If the component carrier carries both Release 8 and LTE-A systeminformation, the LTE-A WTRU may either use a new type of physicaldownlink control channel (PDCCH) with the existing system informationradio network temporary identifier (SI-RNTI), or alternatively the LTE-AWTRU may use the same PDCCH with a different SIA-RNTI which is the newRNTI for LTE-A created and used by the relevant LTE-A WTRUs.

If the existing SI-RNTI is used to carry system information for LTE-A, anew special downlink control information (DCI) format for SI-RNTI PDCCHmay be used. Currently DCI formats 1C and 1A are used for SI-RNTI forRelease 8. Alternatively, an existing DCI format may be used but withdifferent coding rate/control channel element (CCE) aggregation level,etc.

The RNTI value mapping may be changed in LTE-A to accommodate theintroduction of SIA-RNTI. An example is provided in Table 2 below.

TABLE 2 RNTI Values Value (hexa-decimal) FDD TDD RNTI 0000-00090000-003B RA-RNTI 000A-FFF2 003C-FFF2 C-RNTI, Semi- PersistentScheduling C-RNTI, Temporary C- RNTI, TPC-PUCCH- RNTI and TPC-PUSCH-RNTI FFF3-FFFC (or FFF3-FFFB) Reserved for future use FFFD (orFFFC) SIA-RNTI FFFE P-RNTI FFFF SI-RNTI

The system information for both Release 8 and LTE-A may be scheduledtogether in the same time and frequency domain using the current Release8 scheduling method. This refers to the scenario disclosed herein wherethe SIB-12 and SIB-13 may be scheduled with the same system information(SI) window length as that in Release 8. In case the addition of LTE-ASIBs to the total SI broadcast would cause the staggering SIs to exceedthe shortest periodicity span of 160 ms then the following may apply.

In an example method, frequency resource blocks (RBs) are added to theSI broadcast in the compatible carrier, so that the SI-window length maybe reduced to a limit (e.g. 10) and therefore the staggering of Release8 and LTE-A SIs at certain SFN % T=0 for all Ts, where T is periodicity,would not exceed the shortest SI periodicity, i.e. the NSIBs×W<=(theshortest SI periodicity in subframes, usually 160), where the NSIs isthe total number of SIs (from SIB-2 and up, Release 8 and LTE-A) and Wis the SI-window in sub-frames.

In another method, the frame offset may be added to the schedulingformula such as SFN mod T=(OFFSET-A+FLOOR(x/10)), where OFFSET-A is aLTE-A specific frame offset. Corresponding to this change, the order ofthe LTE-A SIs in the Release 8 scheduling information is counted withrespect to the first LTE-A SI in the SIB-1 scheduling information (notthe order from the first SI for Release 8). The OFFSET-A may take thevalue 18, if the additional LTE-A SI's do not exceed 7 (given they takeSI-window<=20).

Alternatively, both methods outlined herein, i.e. keeping the SI-windowshort and providing an offset to LTE-A only SIs on the compatiblecarrier, may be used.

The MIB or SIB extensions may carry possible LTE-A cell configurationinformation such as the number of carriers and/or the anchor carriers,how the downlink and uplink carriers or anchor carriers are linked andtheir frequency locations (E-UTRA Absolute Radio Frequency ChannelNumber (EARFCN) numbers). The carrier frequencies may be labeled such as1, 2, . . . , N to allow rapid identification on PDCCHs used for uplinkand downlink grants. The LTE-A WTRU may use the information for uplinkaccess on the linked uplink carrier or anchor carrier.

The information about all of the carriers may be received by the WTRUwith RRC messaging as well.

The time/frequency location of the new MIB/SIBs or extensions to theseis known to the WTRU. This may be achieved by allocating a fixedtime/frequency location to some of these entities, for example, the MIB.This may also be achieved by informing the WTRU of the scheduling ofthese entities, for example, by transmitting this information in SIB1.The WTRU received these entities on the given time/frequency locationdecodes. To unmask the CRC, the WTRU may either use an LTE-A specificRNTI or the same RNTI as is being used in Release 8. After decodingthese entities, the WTRU obtains LTE-A specific system information.

The LTE-A specific information (such as the number of transmit antennas,for example, up to eight or more), should be indicated either byexisting PBCH, new MIBs or new SIBs. The PBCH is further modified tosupport LTE-A specific features (e.g., high order MIMO). The PBCH isillustrated in Table 3 below:

TABLE 3 CRC mask for PBCH Number of transmit antenna ports PBCH CRC maskat eNode-B <x_(ant,0), x_(ant,1), . . . , x_(ant,15)> 1 <0, 0, 0, 0, 0,0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0> 2 <1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,1, 1, 1, 1> 4 <0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1> 8 CRC4

CRC4 is a PBCH CRC mask for the number of transmit antenna ports ateNodeB equal to eight. Knowledge about the number of transmit antennashelps the channel estimation and demodulation of PDCCH and physicaldownlink shared channel (PDSCH) downlink shared channel (DL-SCH) for thesystem information (SIBs) and data demodulation. Described hereinafterare examples with respect to this embodiment.

In an example, if it is a Release 8 backward compatible anchor carrier(Type 1) and only new SIBs are used to transmit LTE-A specific systeminformation, then the first three CRC masks are used for PBCH as shownin Table 3. Information about the number of transmit antennas up to fourmay be indicated. Information about the number of transmit antennas upto eight may be indicated in new SIBs.

In another example, if it is a Release 8 backward compatible anchorcarrier (Type 1) and new MIBs are used to transmit LTE-A specific systeminformation, all of the four CRC masks as shown in Table 3 are used forthe new PBCH. Information about the number of transmit antennas up toeight may be indicated.

In another example, if it is a LTE-A only anchor carrier (Type 3), allthe four CRC masks are used for PBCH. Information about the number oftransmit antennas up to eight may be indicated.

Described herein is a method for handling a Release 8 non-backwardcompatible LTE-A anchor carrier. In this case, a completely newbroadcast channel with new MIBs and SIBs may be used. The LTE-A obtainsthe LTE-A specific system information by decoding these new MIBs andSIBs. The carrier may also contain multicarrier system information, newsynchronization signal, paging, etc. Alternatively, for the LTE-A onlyanchor carrier, the LTE-A MIB and SIBs may use the frequency and timeresources in the same way as they are being used in current Release 8MIB and SIB broadcasts.

In both the Release 8 compatible and non-compatible anchor carriers, theLTE-A WTRU will act on the received system information, e.g. perform theuplink random access over a particular uplink carrier with the time andpreamble selected according to the random access parameters received.

Disclosed now is a second embodiment with a single anchor componentcarrier and several detectable LTE-A component carriers.

In the first example embodiment, the only detectable LTE-A componentcarrier was the anchor carrier. However, it may be also possible thatseveral LTE-A component carriers have the synchronization channel butthey do not carry the system information on the broadcast channel. Thismay be used for the purpose of load balancing. In this case, the WTRUneeds to learn the type of the carrier and a direction mechanism to theanchor component carrier.

If the detected carrier is Release 8 backward compatible, then themethods disclosed herein for the first example embodiment may be used.

If the detected component carrier is a Release 8 non-backward compatibleLTE-A carrier, a small amount of information that contains the type ofthe component carrier and the location of the anchor carrier may besent. In this case, note that the Release 8 broadcast channel is notrequired to be transmitted because the carrier is not backwardcompatible.

The indication of the type of carrier may be carried in the broadcastchannel by defining a new entity similar to a MIB or SIB. The WTRU knowsthe location of this entity in time/frequency and reads this informationin that location. The information may also be encoded with a new RNTI.This information does not result in a large overhead and is just anindication of the type of the carrier and possibly carries the locationof the anchor carrier. As an example, the new entity may be carried inthe central x (x is equal or less than 6) RBs of the 1.25 MHz bandwidth,and on the same OFDM symbols as the Rel-8 MIB is transmitted.

The WTRU decodes the new entity which is carried on a fixedtime/frequency location. After decoding the new entity, the WTRU learnsthe type of the component carrier and possibly the location of theanchor carrier.

Disclosed now is a third embodiment with several anchor componentcarriers. There may be more than one LTE-A component carrier thatcarries the system information in the carrier-aggregated LTE-A cell. Inthis case, the component carriers may carry the same system informationor they may carry possibly different system information. The RACHparameters for each anchor carrier may be different. These possibilitiesare disclosed herein.

In an example embodiment, all anchor carriers carry the same systeminformation. In this case, the information about the whole system may betransmitted on each one of the anchor carriers. For example, the numberof downlink and uplink component carriers, the linkage between thedownlink and uplink component carriers, the random access parameters forthe downlink component carriers, etc. A WTRU may learn the LTE-Aspecific system information by reading the broadcast channel in any oneof the component carriers. Note that all the DL component carriers maybe Release 8 backward compatible. In this case, the methods disclosedfor the first example embodiment may be used.

Alternatively, the DL component carrier that the WTRU detects during thesynchronization process may be considered as a temporary anchor carrierby the WTRU. In this case, the WTRU obtains the random access parametersfrom the temporary anchor carrier, including a temporary UL carrierwhich the WTRU will use for the RACH transmission. Temporary carrierspecific IDs (RNTIs or scrambling sequences) may be applied for therespective DL and UL temporary carriers. With this method,load-balancing may be achieved within a multi-anchor-carrier cell, asWTRUs in the cell may spread/camp on different anchor carriers.

In an example embodiment, anchor carriers carry different systeminformation. Some parts of the system information carried by the anchorcarriers may be different. As an example, if there are two anchorcarriers denoted as Anchor X and Anchor Y, the system informationcarried on Anchor X may include information about the uplink componentcarrier linked to this anchor carrier and possibly any other downlinkcomponent carrier linked to the same uplink component carrier. Asanother example, random access parameters corresponding only to Anchor Xand the linked uplink component carriers, may be transmitted only onAnchor X. If there are additional downlink component carriers linked tothe same uplink component carrier, random access parameters for thesecarriers may also be transmitted on Anchor X. Note that there may bedifferent random access parameters for the downlink component carrierslinked to the same uplink component carrier so that the NodeB maydifferentiate which downlink component carrier the WTRU is listening to.

In this case, the WTRU learns part of the system information by readingthe broadcast channel on one of the anchor carriers. The rest of thesystem information may be learnt by higher layer signaling after the RRCconnection is established.

It should be noted that based on the assumption that only the anchorcarrier transmits the required system information including the randomaccess parameters, the WTRU starts the random access attempt on theuplink component carrier linked to the anchor component carrier. Inanother method, as disclosed in the first embodiment, the WTRU may startthe random access attempt on a non-anchor Release 8 component carrierand then be redirected to the anchor component carrier by RRC signalingor random access messages.

Disclosed now is a method for redirecting the WTRU to an anchorcomponent carrier from a Release 8 carrier. To redirect a WTRU from aRelease 8 non-anchor carrier to one of the anchor carriers, the methodsdisclosed with respect to the first phase of the first embodiment may beused. It is important to note that when there are several anchorcarriers, the WTRU may be redirected from the Release 8 carrier to anyone of the anchor carriers. To achieve this, the location information ofall anchor carriers may be transmitted on the Release 8 carriers and theWTRU selects one of the anchor carriers. The selection may be based on aspecific criterion, for example a preferred carrier frequency, bestdownlink link quality (such as Reference Signal Received Power (RSRP))or the selection may be random. Further, the WTRU may be redirected fromthe Release 8 carrier to any one of the anchor carriers by transmittingthe location of a single anchor carrier on the Release 8 carrier.

Disclosed hereinafter is a method for redirecting the WTRU to one anchorcomponent carrier from another anchor carrier. It may be also possiblethat the WTRU is directed from one anchor component carrier to anotheranchor component carrier. This may be needed, for example, to achieveload balancing within a multi-anchor-carrier LTE-A cell. It is furthernoted that the LTE-A anchor is responsible for all WTRU idle modeoperations. Example methods for addressing this are disclosed herein.

According to an example method, the network may direct the WTRU toanother anchor carrier from the current component carrier using somekind of redirection in message 4 of the random access procedure orpossibly as part of the Non-Access Stratum (NAS) messages. In this case,the WTRU decodes the message and if there is a redirection command, theWTRU moves to the anchor component carrier indicated in the command. Inthe command, the WTRU might receive the new anchor carrier's centerfrequency number, a frequency offset to the current anchor carrier, orsome other means to locate the new anchor.

According to another example method, the WTRU may receive and explicitredirection command via an RRC message at connection release when theWTRU goes from connected mode to the idle state. In the command, theWTRU may receive the new anchor carrier's center frequency number, afrequency offset to the current anchor carrier, or some other means tolocate the new anchor.

According to another example method, one of the MIB/SIBs may post acell-load factor and one or more target carrier frequencies of theanchor component carriers. If the current anchor carrier's load factoris above a certain threshold (or link quality is below a threshold), theWTRU may automatically select one of the target anchor componentcarriers indicated in the system information and move to that carrier.This procedure applies to the idle mode.

Redirection from one anchor component carrier to another anchorcomponent carrier may also happen in the connected mode. The methodsdisclosed for idle mode are equally applicable.

Disclosed hereinafter are the types of information that could bedifferent on different anchor carriers. Each anchor carrier may carryinformation about the linked uplink component carrier. Further, eachanchor may carry information about the other downlink componentcarrier(s) linked to the same uplink component carrier as the anchorcarrier, and each anchor carrier may carry different random accessparameters. When several anchor carriers are linked to the same uplinkcomponent carrier, the same random access parameters may also be used.

Each anchor carrier may have different SIBs, especially SIB2 thatincludes information about radio resource configuration like MIMOconfiguration, uplink control channel configuration, etc. This SIBincludes the random access parameters as well. Note that in LTE-A,another SIB may be used to carry this kind of information.

In the case where the LTE-A anchor carrier addresses the WTRU idle modepaging, then the paging cycle or DRX cycle length may be configureddifferently from anchor carrier to anchor carrier. Other idle modepaging related parameters that may be different is the “number ofsub-frame occasions for paging in a paging frame”, i.e., the current Nsparameter in idle mode paging and the paging sub-frame patterndefinition table.

The WTRU learns these parameters and system information by reading thebroadcast channel transmitted on the anchor carrier. Although there maybe several anchor component carriers in an LTE-A cell, the WTRU mightneed to lock onto only one of them at a given time for systeminformation purposes.

Disclosed hereinafter are methods for addressing system informationmodifications. When there is a change in the system information (SI),the WTRU may get notification by two example methods. In an examplemethod, the WTRU may check the PDCCH for a particular RNTI that is usedto transmit system modification commands, for example, SI-CHG-RNTI. Thiscommand may be transmitted periodically and could consist of anindication flag. The command may also indicate which particular SIBs aremodified by using a bitmap provided there is an SI change. The WTRUperiodically looks for the PDCCH command with a given RNTI. Aftersuccessfully decoding the command, if there is an SI change, the WTRUreads the modified SIB on the scheduled time/frequency location for thatSIB. In another method, the WTRU may check the paging message to see aspecial indicator change.

For system information modifications, the following methods may beapplicable. In an example method, the paging cycle in connected mode maybe the same for all of the component carriers or can be different fordifferent component carriers when it provides paging.

In another method, when the network wants to change the systeminformation, it may page the WTRU only on the anchor component carrier.Hence the WTRU needs to monitor its paging cycle only on the anchorcomponent carrier.

In another method, the WTRU, depending on the paging cycle which bestsuits its DRX cycle, may choose the anchor carrier which it wants tomonitor. The monitoring can happen in the WTRU DRX on-duration andactive-time that overlaps the paging cycle on that chosen anchor carrierin order to save power.

In another method, the WTRU may calculate the system modificationperiods based on the anchor component carrier. The system modificationperiod may be calculated as SFN mod N, where N may be the modificationperiod coefficient in frames, which may be received only on the anchorcomponent carrier.

In another method, once the WTRU receives the page, it may startreceiving the new system information from the modification period. Forthe duration when the WTRU is receiving the new system information, theWTRU may stop listening to the other component carriers and only listento data from the anchor component carrier simultaneously along withreceiving the SIs over the BCCH.

In another method, the WTRU may also monitor the value tag of SIB-1 onthe anchor component carrier so that it does not have to read the pagingmessage on each paging cycle.

For the methods disclosed herein, if there are many anchor componentcarriers, the WTRU may be told which anchor component carrier the WTRUneeds to listen to for system information change and/or paging.Alternatively, if all the anchor carriers are synchronized from thenetwork perspective, then the WTRU may listen to all anchor componentcarriers for this information.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A method implemented by a wirelesstransmit/receive unit (WTRU), the method comprising: receiving a firstradio resource control (RRC) message comprising carrier aggregationinformation, the carrier aggregation information comprising anindication that downlink control information for downlink transmissionson a first component carrier will be received via a second componentcarrier, wherein the WTRU receives, via the second component carrier, anindication of which orthogonal frequency division multiplexing (OFDM)symbols of a subframe include a physical downlink shared channel (PDSCH)region for the WTRU to decode the downlink transmissions on the firstcomponent carrier; receiving a physical downlink control channel (PDCCH)transmission on the second component carrier, wherein the PDCCHtransmission comprises a downlink grant and an index indicating whichcomponent carrier is to be used for carrying a physical downlink sharedchannel (PDSCH) transmission associated with the downlink grant;determining the PDSCH transmission is to be received on the firstcomponent carrier based on the index included in the PDCCH transmissionreceived on the second component carrier; and receiving the PDSCHtransmission on the first component carrier in accordance with thedownlink grant included in the PDCCH transmission received on the secondcomponent carrier.
 2. The method as in claim 1, wherein the index isincluded in a carrier indicator field of the PDCCH transmission.
 3. Themethod as in claim 1, wherein each of the first component carrier andthe second component carrier include a respective PDCCH.
 4. The methodas in claim 1, wherein each of the first component carrier and thesecond component carrier support operation of Long Term Evolution (LTE)Release 8 WTRUs.
 5. The method as in claim 1, wherein the carrieraggregation information indicates that multiple component carriers areto be scheduled via PDCCH transmissions sent on the second componentcarrier.
 6. The method as in claim 1, wherein the second componentcarrier does not include a transmitted PDCCH.
 7. The method as in claim1, wherein the second component carrier is a primary component carrierfor the WTRU.
 8. The method as in claim 7, wherein the primary componentcarrier is a component carrier that the WTRU initially connected to. 9.The method as in claim 1, wherein the indication of which OFDM symbolsof a subframe include the PDSCH region for the WTRU to decode thedownlink transmissions on the first component carrier comprises anindication of a number of OFDM symbols that should be assumed to includecontrol information at the beginning of the subframe.
 10. The method asin claim 9, wherein the indication of the number of OFDM symbols thatshould be assumed to include the control information at the beginning ofthe of the first component carrier is transmitted via a physical controlformat indicator channel (PCFICH) of the second component carrier.
 11. Awireless transmit/receive unit (WTRU) configured, at least in part, to:receive a first radio resource control (RRC) message comprising carrieraggregation information, the carrier aggregation information comprisingan indication that downlink control information for downlinktransmissions on a first component carrier will be received via a secondcomponent carrier, wherein the WTRU is configured to receive, via thesecond component carrier, an indication of which orthogonal frequencydivision multiplexing (OFDM) symbols of a subframe include a physicaldownlink shared channel (PDSCH) region for the WTRU to decode thedownlink transmissions on the first component carrier; receive aphysical downlink control channel (PDCCH) transmission on the secondcomponent carrier, wherein the PDCCH transmission comprises a downlinkgrant and an index indicating which component carrier is to be used forcarrying a PDSCH transmission associated with the downlink grant;determine the PDSCH transmission is to be received on the firstcomponent carrier based on the index included in the PDCCH transmissionreceived on the second component carrier; and receive the PDSCHtransmission on the first component carrier in accordance with thedownlink grant included in the PDCCH transmission received on the secondcomponent carrier.
 12. The WTRU as in claim 11, wherein the WTRU isconfigured to refrain from attempting to decode PDCCH transmissiontransmitted on the first component carrier based on receiving thecarrier aggregation information.
 13. The WTRU as in claim 11, whereincontrol information for WTRUs supporting carrier aggregation and controlinformation for WTRUs lacking support for carrier aggregation ismultiplexed on the PDCCH of the second component carrier.
 14. The WTRUas in claim 13, wherein the control information for WTRUs supportingcarrier aggregation and the control information for WTRUs lackingsupport for carrier aggregation is multiplexed on the PDCCH of thesecond component carrier in a hybrid frequency division multiplexing(FDM)/time division multiplexing (TDM) manner.
 15. The WTRU as in claim11, wherein the index is included in a carrier indicator field of thePDCCH transmission.
 16. The WTRU as in claim 11, wherein the WTRU isconfigured to detect the PDCCH transmission using blind decoding.
 17. Abase station configured, at least in part, to: determine that downlinkcontrol information for a first component carrier is to be transmittedto a wireless transmit receive unit (WTRU) using a physical downlinkcontrol channel (PDCCH) of a second component carrier; send a firstradio resource control (RRC) message comprising carrier aggregationinformation to the WTRU, the carrier aggregation information comprisingan indication that the downlink control information for downlinktransmissions on the first component carrier will be sent to the WTRUvia the PDCCH of the second component carrier, wherein the base stationis configured to send, via the second component carrier, an indicationof which orthogonal frequency division multiplexing (OFDM) symbols of asubframe include a physical downlink shared channel (PDSCH) region forthe WTRU to decode the downlink transmissions on the first componentcarrier; send a PDCCH transmission to the WTRU on the second componentcarrier, the PDCCH transmission comprising a downlink grant and an indexindicating which component carrier is to be used for carrying a PDSCHtransmission associated with the downlink grant, wherein the indexincluded in the PDCCH transmission indicates that the first componentcarrier is to be used by the WTRU for receiving the PDSCH transmissionassociated with the downlink grant; and receive the PDSCH transmissionon the first component carrier in accordance with the downlink grantincluded in the PDCCH transmission received on the second componentcarrier.
 18. The base station as in claim 17, wherein the index isincluded in a carrier indicator field of the PDCCH transmission.
 19. Thebase station as in claim 17, wherein each component carrier utilized bythe base station for communicating with the WTRU is scheduled using thesecond component carrier.
 20. The base station as in claim 17, whereinthe base station is further configured to send an indication to the WTRUthat the downlink control information for the first component carrierwill be shifted to a different component carrier.